No country today exists - or could exist - in isolation from other countries. Countries rely on other countries for supply of raw materials, manufactured goods and as markets for their own exports…all meaning that the quality of relations between countries needs to remain relatively strong and stable.
Any would-be politician with any level of intelligence realises that the interests and strength of his own country depend at least partially on the stability and continued existence of like-minded trading partner countries, and is in no way disloyal to his own country by expressing support for those other countries.
